One of the most popular online “haul” videos was made by the YouTube star and “influencer” Zoella. A haul video, for those who find their own shopping tedious let alone thinking about other people’s shopping, is where a young woman (usually) unpacks the bounty from a shopping trip. They are strangely watchable and they are certainly popular.

Zoella’s most watched video – entitled Huge Spring Primark Haul, in which she talks the viewer through 24 purchases from the cheap high street store – has had more than 4.25 million views; she says things such as “You can never have too many pyjama bottoms, especially from Primark because they are such good value for money and you get a lot. A lot.”

You don’t have to be even a vaguely committed environmentalist to feel dismayed at our addiction to cheap, fast fashion and the amount that is produced each year – 100 billion garments. In March, it was reported that the high street chain H&M had $4.3bn of unsold clothes. Meanwhile, Amazon is pushing its way into fashion retail.

The industry is – thanks to the boom in fast fashion boom that has been growing since the 2000s – one of the most polluting. A BBC documentary, Fashion’s Dirty Secret, to be screened on Monday night, highlights many of the horrors and also shows how the public underestimates its environmental impact.

Presenter Stacey Dooley travels to the Aral sea – more of a puddle now, thanks to the water being diverted to irrigate Uzbekistan’s cotton fields. Communities have been destroyed, disease is rife because of carcinogenic dust, and even the weather has been affected. “Did I know cotton was capable of this? Course I didn’t. I had no idea,” says Dooley in the film.

She also goes to Indonesia, where people are washing in, and cooking with, water polluted with toxic chemicals from clothing factories. The big brands, such as Primark and Asos, refused to talk to her, and a government statement was pitiful, so she turned her attention to the so-called fashion influencers on social media, “to confront another part of the problem” – the constant hunger for new things and the normalisation of disposable clothing. Could influencers, she asks, be one way of getting us to change the way we shop?

It seems optimistic, but possible. “They don’t just use their platforms to sell aesthetics, they’re also using their platforms for a positive change,” says the style blogger and writer Susie Lau, who appears in the documentary. “They have a sway over many issues. A lot of influencers will be very aware of their voices.”

In the film, the influencers Dooley meets seem horrified by her footage. “We don’t want to be promoting certain brands or fast fashion knowing this is going on… we’re not doing that on purpose,” says the lifestyle blogger Niomi Smart, who has 1.6 million Instagram followers.

“It’s all about allowing people to know they can wear the same outfit more than once, or swap clothes. Let’s talk about this. What can we do to make more of an effort towards being more conscious of the environment?”

The YouTube haul video is one of the most conspicuous manifestations of consumer fashion culture, but it is Instagram which is the most powerful platform for fashion influencers, such as Chiara Ferragni, Julia Engel and Danielle Bernstein and the brands clamouring to work with them. Figures from InfluencerDB, a marketing analysis company, estimated that the top 20 fashion brands received more than $650m of “earned media value” (what they would have spent on traditional advertising) from exposure on Instagram by influencers paid to promote their products.

“There is so much fashion in the marketplace that it’s hard to make a choice, so the influencer provides a shortcut,” says Patsy Perry, senior lecturer in fashion marketing at the University of Manchester. Fashion brands increasingly work on getting products to consumers as fast as possible, sometimes in as little as two weeks. “The cycle is speeded up – we buy more stuff, not keep it as long, and then we’re on to the next trend,” says Perry.

There has been a bit of a backlash against hauls, says Orsola de Castro, founder and creative director of the Fashion Revolution movement, which has worked with “haulers” to encourage a more sustainable approach. The response so far has been mixed, she says. “I’m afraid many go back to what they were doing.”

For every influential Instagrammer who decides to champion more sustainable fashion, there must be tens more eager to focus on the fast fashion gap. De Castro laughs. “I think more like thousands. This is a new business model and it’s at its peak so it is difficult to turn it around and make it more sustainable because ultimately we’re talking about slowing down, and for social media and the influencers it’s the opposite – they’re running at maximum speed.”

Kate Nightingale, a consumer and fashion psychologist, cautions against the idea that influencers can change the industry alone. “It depends how much the industry will be listening,” she says. “I work with brands and some listen to consumers, some pretend that they do and some don’t care about it at all.” But the power doesn’t only reside with the influencer and consumer, she says. “It’s the investors, the structure of the company, all of those things have to change for the brands to start changing the whole industry.”

Documentary maker Stacey Dooley at the shores of the Aral sea, which has been depleted to support the cotton trade. Photograph: Olivia Strong/BBC

Brands are listening – she points to Primark stocking sustainable cotton as one small example – but changing the industry will not be easy. People are used to cheap fashion, and new collections every few weeks when it used to be “just two or four maximum a year”. Perry adds that it’s hard to imagine the huge fashion brands switching to a business model “that is not based on selling more stuff. It’s not really on the agenda of companies.”

Is it unfair to blame influencers for the rise of disposable fashion?

Lau thinks so. “I think fashion as a whole, we’re all in the business of selling new things to consumers, it’s not influencers alone,” she says. “The only difference is that[But] influencers operate through social media and it can feel like you’re seeing new clothes, constantly. The speed of it has changed, and the platforms have changed, but the industry as a whole has a lot to answer for. If you look at fashion magazines, how much is dedicated to sustainable fashion? Or how many of their advertisers are supportive of sustainable fashion? So I think this is an issue that the whole of the industry needs to tackle.”

It would be wrong to overstate the singular power of influencers, she says. “If American Vogue suddenly decided not to shoot any collection that didn’t [use] materials that were sustainably sourced, that would have a much bigger sway than if influencers suddenly decided to boycott fast fashion.”

She adds “I don’t necessarily believe [that] all fast fashion is evil, I think companies can change their processes and they have the scale and financial clout to do it.”

De Castro thinks people are waking up to the environmental impact of their clothing choices, and she hopes fast fashion will become demonised in the same way plastic recently has. “I think it’s going to go that way with clothes,” she says. “Within a few years, we will be so aware of this mass of stuff that we’re buying and getting rid of that it’s not going to be so cool for a hauler to say ‘I bought all this’. [This] won’t look fashionable once we’ve got issues with water, for instance. When it becomes visible, there will be a reaction against it.”